1. Field of the Invention
The present invention relates to a method for the fabrication of GaN-based vertical cavity surface-emitting devices with current confinement structure, in particular, to a silicon-diffusion defined current confinement structure.
2. Description of Related Art
Semiconductor laser, due to its small size, high efficiency, high cost-performance, and low operating voltage, is suitable for fiber optic communication, high-density optical storage, high-speed laser printing, and biomedicine research, and has become one of important active photoelectric components.
Conventional semiconductor laser structure includes vertical cavity surface-emitting laser (VCSEL) and edge-emitting laser (EEL). In comparison, vertical cavity surface-emitting laser has more advantages than edge-emitting laser, including lower threshold current, symmetrical circular laser beam, smaller divergence angle, and easier to be made into a two-dimensional array, especially suitable for use in fiber-optic communications.
Traditional vertical cavity surface-emitting laser has different confinement structures, including etched air-post structure, buried heterostructure, ion implanted structure and oxide confined structure in four categories.
The wavelength of a vertical cavity surface-emitting laser may vary from infrared light to visible and ultraviolet light with different materials. Currently, the development of the VCSEL that uses GaAs (Gallium Arsenide) material to exhibit the near-infrared light wavelength in a range from 0.78 μm to 0.98 μm has been quite mature, and the VCSEL of long-wavelength light in a range from 1.3 μm to 1.55 μm that uses GaAsInP material is becoming mature rapidly. However, the development of the VCSEL that uses GaN (Gallium Nitride) material to exhibit the short-wavelength in a range from 0.36 μm to 0.55 μm has been relatively slow, largely because of the lack of lattice-matched GaN substrate material and of lattice-matched GaN-based high reflectance DBR (distributed Bragg reflector) epitaxial growth. Meanwhile, the gain of the active layer material itself is low, thus GaN vertical cavity surface-emitting laser requires a better current confinement structure to enhance carrier concentration, and good optical surface coating of high-reflectance and low-loss to reduce the laser threshold.
In the prior art, U.S. Pat. No. 5,226,053 disclosed the use of vertical resonant-cavity and distributed Bragg reflector, but it didn't teach a silicon-diffusion defined current confinement structure. Another prior art, U.S. Pat. No. 8,774,246 disclosed the use of depleted hetero junction current blocking region (DHCBR) as an instrument for current confinement. It is different from our design which uses diffusion-produced homo-junction to form a current blocking structure.